The Automatic Computing Engine (ACE) was an early electronic stored-program computer design produced by Alan Turing at the invitation of John R. Womersley, superintendent of the Mathematics Division of the National Physical Laboratory (NPL). The use of the word Engine was in homage to Charles Babbage and his Difference Engine and Analytical Engine. Turing's technical design Proposed Electronic Calculator was the product of his theoretical work in 1936 "On Computable Numbers" and his wartime experience at Bletchley Park where the Colossus computers had been successful in breaking German military codes. In his 1936 paper, Turing described his idea as a "universal computing machine", but it is now known as the Universal Turing machine.
Turing drew up the initial design for the Automatic Computing Engine in 1945. The design was approved by the National Physical Laboratory in 1946. Construction of the ACE proceeded slowly, and it was not until 10 May 1950 that the Pilot Model ran its first program. Turing himself had by this time left the National Physical Laboratory for Manchester University. The Pilot Model ACE was London's first electronic computer and the third stored-program computer to function in Britain. With a clock speed of 1 MHz it remained for some time the fastest computer in the world. DEUCE, the production version of the Pilot Model ACE, was built by the English Electric Company. In total more than 30 were sold. The NPL's